Rotary disc filters utilize backwashing systems to periodically clean the filter media disposed on opposite sides of rotating disc-shaped filter members. Generally, when backwashing is needed, the rotary drum supporting the disc-shaped filter members is rotated. The backwashing system sprays a backwash at a pressure of approximately 100 psi, for example, onto the exterior surface of the filter media. This causes suspended solids secured on the inside of the filter media to be dislodged and fall into a collection trough inside the drum of the disc filter. While standard pressurized backwash is adequate in many cases to keep the filter media clean and maintain the hydraulic capacity under most conditions, experience has shown that certain process conditions will result in a fouling effect on the filter media that is not removed by standard backwash. This fouling effect may occur as a result of biological growth, mineral precipitation, build-up of chemical residue (such as polymer), or other various process conditions that may result in fats, oils, greases, etc. coming into contact with the filter media. When this occurs, the hydraulic capacity of the filter media is significantly reduced as a result of the fouling.
When there is significant fouling of the filter media, there is a need for chemical cleaning which is sometimes referred to as filter media regeneration. While chemical cleaning is known, one of the drawbacks of conventional rotary disc filters today is that cleaning by conventional backwash approaches and regenerative cleaning, such as by utilizing chemicals, are generally disconnected and are not integrated and controlled in relationship to each other. This often leads to inefficient backwashing and chemical cleaning regimes.
Moreover, when it comes to regenerative cleaning, it is often difficult to determine the appropriate time when regenerative cleaning is needed or required and also it is difficult to determine how to implement regenerative cleaning in a way that does not substantially impact the ongoing performance of the rotary disc filter. In the past, regenerative cleaning has been employed when the disc filter is off-line, or not in use. This is costly and expensive. Therefore, there has been and continues to be a need for an integrated backwash and regenerative cleaning system that is automatically controlled and wherein regenerative cleaning can be carried out in a way that does not substantially detract from the capacity of the rotary disc filter.